Influence of plasma functionalization of poly(propylene) with acrylic acid on the nucleation of CaCO3

Poly(propylene) surfaces were modified by polymerization of acrylic acid using an RF plasma technique. Whereas a stable and reproducible hydrophilicity is obtained even after short treatment times, the thickness of the deposited layer, and thus the concentration of -COOH functional groups per substrate surface area, increases with plasma exposure time. The modified-poly(propylene) samples were exposed to aqueous solutions supersaturated with respect to CaCO3. Even though the polymer surfaces show a significant affinity for the adsorption of CA(2+) ions, the density of nucleation sites for calcite is reduced in comparison to untreated poly(propylene). This result can be explained by the special conditions in porous ("gelatinous") growth media and high disorder provided by the plasma-polymerized layers.